Device for casting acrylic sheets

ABSTRACT

A temperature conducting metallic member having hollow upper and lower sections thereof vertically spaced apart by columns and a plurality of support bars connected to said upper and lower sections, said upper section having spray means and liquid inlet means therein and said lower section having liquid removal means therein, is disclosed.

United States Patent Cate et a1.

[451 Aug. 1,1972

DEVICE FOR CASTING ACRYLIC SHEETS Inventors: Alan Clifford Cate, Springvale; Roy Charles Gordon, Kenneburk, both of Maine American Cyanamid Company, Stamford, Conn.

Filed: M1 1970 Appl. No.: 98,254

Assignee:

US. Cl. ..425/86, 425/338, 425/405,

425/407, 425/425, 249/79, 249/160 Int. Cl. ..B29c 5/00,'B29d 7/02 Field of Search ..264/102, 313; 18/26 R, 38, 18/39; 249/79, 81, 189, 192

' References Cited UNITED STATES PATENTS 3,579,738 11/1969 Beattie ..18/39 X 2,522,360 9/1950 Hamilton ..249/192 .X 3,448,790 6/1969 Maskall ..249/ 79 X 2,067,580 1/1937 Rohm ..264/313 3,551,541 12/1970 Rossetti ..18/26 R-X 3,156,015 1 H1964 Harrison ..18/3'8 3,550,206 12/1970 Von Der Heide ..18/39 X Primary Examiner-J. Howard Flint, Jr. Att0rney-Frank M. Van Riet 5 7] ABSTRACT A temperature conducting metallic member having hollow upper and lower sections thereof vertically spaced apart by columns and a plurality of support bars connected to said upper and lower sections, said upper section having spray means and liquid inlet means therein and said lower section having liquid removal means therein, is disclosed.

2 Claims, 2 Drawing Figures Pmmmws 1 I 3.680.991

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INVENTORS ALA/V a 0475 R0) 0. coma/v BY Mm.

A 7' TOR/VE Y DEVICE FOR CASTING ACRYLIC SHEETS BACKGROUND OF THE INVENTION In the typical casting of acrylic sheet, molds formed by two glass plates which are separated by a peripheral gasket sealer and clamped together, are filled with casting syrup through a gap left in the gasket. The casting 'syrup ismade up of partially polymerized monomer which, once placed in the mold, is heated for a considerable length of time and thereby converted to a solid plastic sheet.

.A semicontinuous process for the production of such sheets has recently become more commercially attractive than prior methods whereby the sealed molds or cells were piled atop one another and placed into an oven on a mechanical conveyor truck.

This semicontinuous process comprises a series of casting cells vertically suspended from and movable along an elevated support track. Between each casting cell is positioned a temperature control zone. A heated liquidis allowed to enter into the area between the casting .cells which is defined by said temperature control zone and thereby causes polymerization of the materials in the cell. A typical vertical casting apparatus and method of this type is disclosed in British Pat. No. 1,168,946. A second, less sophisticated procedure is described in U.S. Pat. No. 2,067,580, which patents are hereby incorporated herein by reference.

While these vertical prior art systems have generally proven more efficient than the horizontal-oven casting methods, they too suffer from a series of problems which tend to distract from their otherwise attractive commercial outlook. One of these problems is the large SUMMARY We have now discovered a unique improved apparatus for the vertical casting of acrylic sheets, the use of which obviates various problems previously experienced utilizing prior art techniques. Our system overcomes the necessity of filling and emptying the temperature control zones each time a different temperature is required in the apparatus. Also, the outward bowing of the glass plates of the casting cell caused by the monomer syrup is prevented as is the hydrostatic pressure which usually results when the temperature control zone is filled with heating or cooling liquid. By the use of our novel system, less heating and cooling liquid is needed and consequently less energy is used to raise or lower the temperature of the liquid. A further advantage of our system resides in the faster rate of temperature change effected because the heating and cooling liquid is in direct contact with the glass cell plates, the velocity of the liquid impinging down the glass plates resulting in better heat transfer.

BRIEF DESCRIPTION OF THE DRAWING The drawing,

FIG. 1, depicts aside view of the temperature conducting member of the present invention while FIG. 2 is a sectional view along line 2 of FIG. 1 and depicts a complete polymerization zone of a vertical casting apparatus wherein the temperature conducting members andtheir relationships to the glass casting cells are shown.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS The temperature conducting member of our invention, as depicted in FIG. 1, is comprised of hollow upper section 1 and hollow lower section 2, said sections being vertically spaced apart by outer separating columns 3 and 4 which may be solid but are preferably hollow in order to lighten the total weight of the member. If hollow, the interior of columns 3 and 4 may or may not connect with the interior of sections 1 and 2. A plurality of rigid support bars 5, parallel to said columns 3 and-4, are positioned between and attached to sections 1 and 2. Upper section 1 is fitted with spray means in the form of a plurality of nozzles 7 or other devices, each preferably alternately positioned between bars 5. Lower section 2 has fluid outlet means in the form of holes 8 therein, there preferably being at least one hole 8for each nozzle 7. Upper section 1 is fitted with fluid inlet means 9 while lower section 2 is fitted with fluidremoval means 10. Columns 3 and 4, as well as bars'5, have means 11 therein to maintain the pressure in the cavity 16 formed by the members and the glass mold, as described below, relatively constant.

In use, the member represented by FIG. 1 functions to heat up or cool down a glass casting cell filled with casting syrup. This function is accomplished by feeding cold or hot liquid into upper section 1 via inlet means 9. Liquid may also be fed into the opposite end of section 1 via similar means, not shown, if desired or necessary. The liquid flows throughout the length of section 1, under pressure, and is forced through nozzles 7. A film of liquid is sprayed by the nozzles onto the exterior faces of the outer glass plates of the glass casting cell with which the entire assembly or member is in contact. The impinged liquid flows downwardly over the plates, thereby cooling or heating the contents of the cell and thereafter flows through the fluid outlet means, i.e. holes 8, into lower section 2 and out fluid removal means 10. The opposite end of section 2 may also contain a fluid removal means, not shown. If the interior of columns 3 and 4 are connected to sections 1 and 2, liquid flows through said columns and thereby forms an area of peripheral cooling or heating around the outside edge columns. Atmospheric pressure is maintained throughout the member via openings ll.

In FIG. 2,'a side view of a plurality of casting zones in combination-with a series of temperature conducting members is shown in broken cross-section across line 2 of FIG. 1. Upper and lower sections 1 and 2 are shown, nozzle 7 being connected to upper section 1 via outlet 7a and lower section 2 having liquid outlet 8 therein. Bar 5 is shown extending beyond the outer planes of sections 1 and 2 to such a degree as to come into direct contact with glass plates 14, the amount of compression of compressible sealing means 12 governing the distance the bar extends beyond said planes. The glass plates 14, sealing means 12 and the entire temperature conducting member form a cavity 16 (FIG. 1) for retaining fluid which sprays from nozzle 7. Additional glass plates 17 and 18 are shown separated from each other and plate 14 by two other compressible sealing means 15 and 19 which are positioned around the inner periphery of the pairs of glass plates 14 and 17 and 17' l and 19, usually rubbery polymeric gaskets, however,

it is preferred that the top of the chambers be allowed to remain open to the atmosphere as shown by a and 19a. The entire assemblage of casting zones and temperature conducting members usually amounting to 20 or more in number, is then clamped together, via means not shown, so that sealing means 15, 19 and 12 all form liquid tight seals with the component with which they are in contact. Glass plates 14, 17 and 18 and the temperature conducting member are all supported in vertical orientation on a support means not shown and in a manner not shown, but clearly enumerated in the above cited patents, permitting horizontal movement thereof and the mold plates are thereby held in surfacev contact with each exterior face surface of each of said members. The temperature conducting and controlling members are horizontally spaced apart, at a desired distance, as known in the art. The outer face of each of the two end temperature conducting members of the assembly each has a rigid metallic insulated plate thereover, the entire surface thereof providing a support face for pushing means, not shown, which clamp the assemblage together.

Bars 5 prevent the convex buckling of the glass plates of the mold chambers, e.g. 13 and 20, which would otherwise be caused bythe hydraulic pressure of the syrup in the chambers. In the case of forming a cast sheet, hot liquid, usually water, is charged under pres sure into the hollow portion of upper section 1 of each temperature conducting member, through orifice 7a into nozzle 7. The hot water is sprayed onto the surfaces of the adjacent glass mold plates, e. g. 14, and runs downwardly impinged thereon, thereby heating the contents of the molding chamber, e.g. 13. The liquid in the next member is, at the same time heating the contentsof chamber 20 by flowing over the surface of plate 18. The liquid is removed from the cavity 16 via outlet 8 and removal means 10 and is recirculated through a heating unit, not shown, back to top section 1 of each member. Each member may be individually connected to a heating or cooling source or, more preferably, the members may be connected in series to the same source.

After polymerization is complete, cold water is circulated through the apparatus exactly as described above in regard to the hot water to cool the polymerized sheets which are then recovered by opening the apparatus in a manner known in the art.

We claim:

1. In an apparatus for the casting of resin sheets from polymerizable flowable material, comprising, incombination, a plurality of temperature conducting metallic members, means for moveably supporting said members in vertical orientation with the largest exterior areal face surfaces thereof horizontally spaced from each other and in parallel confronting relationship, a plurality of horizontally spaced glass mold plates being moveably supported in vertical orientation with and in between each 'of said members, each of said largest areal faces of each of said members being arranged in direct temperature transfer relationship with the entire exterior face surface of a glass mold plate, means for holding a mold plate in surface contact with each of said largest areal exterior face surfaces of each of said members and for affording horizontal movement of said held mold plate from said members, compressible sealing means disposed between, around at least three edges of the periphery thereof and in contacting relationship with each interior face of each adjacent pair of said mold plates thereby defining in combination with said mold plates a glasslined mold chamber adapted for receiving and holding a supply of polymerizable flowable material therein, adjustable means for horizontally spacing said members apart, means for pushing said members toward one another, two of said members forming the end sections of the polymerization area of the apparatus, the outer face of each end member having a rigid, metallic insulated plate over the entire surface thereof to provide a support surface for said pushing means, and means for circulating liquid through said members, the improvement wherein said temperature conducting metallic. members are open faced and comprise a hollow upper section and a hollow lower section, said sections being spaced apart vertically at the ends thereof by outer separating columns whereby the resultant members conform in shape and size to said glass mold plates, second compressible sealing means between the largest areal exterior faces of the outer glass mold plates and said members at the peripheral edges thereof, said second sealing means and said members defining, in combination with said mold plates, a cavity for retaining liquid, a plurality of rigid support bars parallel to, between and extending beyond the outer planes of said separating columns and connected to said hollow upper and lower sections and adapted to maintain the continuing integrity of said mold chamber, spray means in said upper hollow section adapted to receive liquid from said upper hollow section and dispense said liquid into said cavity and onto said glass mold plates, liquid removal means in said lower hollow section, liquid inlet means in said upper hollow section, liquid outlet means in said lower hollow section and means in said outer separating columns and said support bars to maintain the pressure throughout said cavity.

2. 'An open faced, temperature conducting member comprising a hollow upper section and a hollow lower section, said sections being spaced apart vertically at the ends thereof by outer separating columns, a plurality of rigid support bars parallel to, between and extendliquid inlet means'in said upper section, liquid outlet means in said lower section and means in said outer separating columns and said support bars to maintain pressure. 

1. In an apparatus for the casting of resin sheets from polymerizable flowable material, comprising, in combination, a plurality of temperature conducting metallic members, means for moveably supporting said members in vertical orientation with the largest exterior areal face surfaces thereof horizontally spaced from each other and in parallel confronting relationship, a plurality of horizontally spaced glass mold plates being moveably supported in vertical orientation with and in between each of said members, each of said largest areal faces of each of said members being arranged in direct temperature transfer relationship with the entire exterior face surface of a glass mold plate, means for holding a mold plate in surface contact with each of said largest areal exterior face surfaces of each of said members and for affording horizontal movement of said held mold plate from said Members, compressible sealing means disposed between, around at least three edges of the periphery thereof and in contacting relationship with each interior face of each adjacent pair of said mold plates thereby defining in combination with said mold plates a glass-lined mold chamber adapted for receiving and holding a supply of polymerizable flowable material therein, adjustable means for horizontally spacing said members apart, means for pushing said members toward one another, two of said members forming the end sections of the polymerization area of the apparatus, the outer face of each end member having a rigid, metallic insulated plate over the entire surface thereof to provide a support surface for said pushing means, and means for circulating liquid through said members, the improvement wherein said temperature conducting metallic members are open faced and comprise a hollow upper section and a hollow lower section, said sections being spaced apart vertically at the ends thereof by outer separating columns whereby the resultant members conform in shape and size to said glass mold plates, second compressible sealing means between the largest areal exterior faces of the outer glass mold plates and said members at the peripheral edges thereof, said second sealing means and said members defining, in combination with said mold plates, a cavity for retaining liquid, a plurality of rigid support bars parallel to, between and extending beyond the outer planes of said separating columns and connected to said hollow upper and lower sections and adapted to maintain the continuing integrity of said mold chamber, spray means in said upper hollow section adapted to receive liquid from said upper hollow section and dispense said liquid into said cavity and onto said glass mold plates, liquid removal means in said lower hollow section, liquid inlet means in said upper hollow section, liquid outlet means in said lower hollow section and means in said outer separating columns and said support bars to maintain the pressure throughout said cavity.
 2. An open faced, temperature conducting member comprising a hollow upper section and a hollow lower section, said sections being spaced apart vertically at the ends thereof by outer separating columns, a plurality of rigid support bars parallel to, between and extending beyond the outer planes of said separating columns and connected to said hollow upper and lower sections and adapted to maintain the continuing integrity of a mold chamber, spray means in the upper hollow section adapted to receive and dispense liquid from said section, liquid removal means in said lower section, liquid inlet means in said upper section, liquid outlet means in said lower section and means in said outer separating columns and said support bars to maintain pressure. 